Reproductive behaviours in a risky world: are mothers trading-off offspring safety for future fitness?

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Behaviour is a highly flexible trait. It varies among individuals as well as within individuals with environmental conditions and among life stages. Predation risk is a major determinant of behavioural variation at all of these levels. However, individuals do not only have to eat without been eaten, they also have to balance the risk of mortality with their investment into reproduction. Some prey animals reduce their parental behaviour and investment under predation risk, as shown for song birds. Whether this pattern can be generalized to other taxa with intense reproductive investment remains to be investigated. Moreover, little is known how animals can balance own survival, current reproductive investment, and future reproductive investment at the same time. Small rodents are a highly suitable study system for studying trade-offs between reproductive and anti-predatory behaviours. They are highly depredated, have flexible mating system (i.e. can mate singly or multiply), and can potentially simultaneously invest into nestling litters (current investment) and pregnancy (future investment). This produces a conflict between caring for the current offspring, and leaving the offspring temporally behind for mating in order to be able to invest into future offspring. With their concurrent and sequential pregnancy and lactation, small rodents are suitable study system to experimentally separate the effects of predation risk on different stages in the life cycle on the trade-off between current reproductive investment (nest guarding) and future reproductive investment (mating behaviour).Here I want to experimentally study the flexibility and constraints of rodent reproductive behaviour in response to predation risk at various life stages: 1) infanticide risk for nestlings (current reproductive investment) on mothers investment into mate search (future reproductive investment);2) predation risk for the mother on her investment into mate search (future reproductive investment) and 3) predation risk for the mother on her mating strategy (monandric or polyandric involving variation in genetic diversity of investment). In all experiments, individual variation in time allocation, physiological responses, space use and mating success will be monitored allowing quantifying both behavioural and fitness consequences. Experiments will be conducted in different spatial and temporal scales: behavioural observations in the laboratory and automated telemetry observations in semi-natural enclosures. Results of the experiments will give novel estimates of the general flexibility of reproductive behaviour and for the first time measure life-history trade-offs of reproduction and mortality risk for individuals in semi-natural settings. A potential contribution of adaptations of reproductive behaviour in a risky world to predator-prey dynamics can be investigated in a second funding phase..